Installing New Stern Tubes using Optical Scope Alignment

2017 January 9

by Chris Brown

When one of our returning customers, an 87 foot Broward yacht discovered that they had significant corrosion on their stern tubes (shaft logs), they asked our running gear experts to help out. Once we removed the shafts from the boat, we were able to get a better idea of what we were dealing with on the stern tubes. The vessel is made of aluminum and was suffering from corrosion to the point where we would need to fabricate new tubes.

Scoping to align stern tube

To accomplish this, we enlisted our machine shop, Straight Line Marine. The machine shop ensured the inner diameter was machined for the cutlass bearings, drilled & tapped for alignment jacking screws and milled out water vents. Once we finished the machining process, it was time to install the new stern tubes back into the boat. The stern tubes have a cutlass bearing on each end so it is critical that the tube be aligned properly to the struts and engines. To ensure that the stern tubes would be in perfect alignment, we used a process called optical scope alignment or “scoping” for short. Scoping is the most advanced method for obtaining a perfect marine shaft alignment with struts, shaft logs, engines or v-drives. Scoping is the latest generation of alignment technology and far more advanced than the old piano wire system and even laser alignments.

Welded stern tube in pace after optical alignment

The twist here is that we used the scoping process to help the welders perfectly place the new stern tubes in the boat. With the welding complete, we were able to finish the job and ensure that the shaft and stern tubes were aligned, guaranteeing a vibration free ride for this valued customer.